After years of deliberating, you finally sign up to run a marathon. In addition to the self-satisfaction you’ll be relishing come 26.2 miles, there’s often another reason why many of us—despite never having run more than a 5K before—register for months of grueling training: It’s bound to (finally!) help us say sayonara to those lingering five pounds, right?

Unfortunately, in spite of the long runs we’re logging, it doesn’t always work out that way. And in some cases, it can even work in reverse, with marathon runners gaining weight instead of losing it.

According to an article in The Science Of Us, there are a few reasons for the mysterious poundage. One study found the concept of “carb loading” is partially to blame, particularly for novice runners. While carbs are important by providing a reserve of energy, this doesn’t necessarily mean “you have a giant plate of spaghetti with four pieces of bread,” Mary Kennedy, an exercise physiologist at the Institute of Lifestyle Medicine, told Meanwhile, other research has found that people often overestimate how hard they’re exercising, with the majority of participants categorizing their exercise as “vigorous” (meaning their heart rate was between 77 and 93 percent of its full capacity) when, in actuality, they were below 75 percent.

Plus, there’s the issue of appetite. As you burn more calories, your hunger will inevitably increase, which often leads to more food consumption (you just ran 20 miles, so why shouldn’t you feel entitled to that burger?). In addition, as one study published in The Journal of Strength and Conditioning Research indicates, many times, weight gain or inability to lose weight is caused by exercisers “compensating” for all the burned energy by eating more.

So how exactly can marathon training double as a weight-loss program? Runner’s World magazine suggests being meticulous about the calories you’re consuming, especially during your post-run meals, by maintaining a log. Also, choose a variety of healthy fats, protein and carbohydrates to stabilize blood sugar and curb cravings and make sure you’re getting quality sleep, as fatigue can wreak havoc on any weight-loss goal.

Have you noticed it’s difficult to lose weight when training for a marathon? What running “diets” have you found to be most effective?



  1. The Science of Us: I Am Training for a Marathon. So Why Am I Getting Fat?
  2. Runner’s World: Three Reasons Why You're Not Losing Weight While Training for a Marathon
  3. The Journal of Strength and Conditioning Research